Landing gear

ABSTRACT

An aircraft landing gear door assembly includes a door, which is moveable to an open position, in which an aperture is exposed, the landing gear being able to be deployed through said aperture, and moveable to a closed position, in which the door is closed across the aperture. The door is arranged for rotational movement of a first type, in which the door rotates about an axis that is substantially parallel to the length of the aircraft, between the closed position and the open position. The door is also arranged for movement of a second type, different from the first type, in which the door rotates, about an axis that is substantially transverse to the length of the aircraft, to a position in which it acts as a fairing to reduce the noise caused by the landing gear or a part thereof. In one embodiment, the second type of movement is rotational movement about an axis that is substantially parallel to the door when in the closed position and the door forms a ramp type fairing. In another embodiment, the second type of movement is rotational movement about an axis that is substantially transverse to the door when in the closed position and the door forms a V-shaped fairing (when viewed from above) with an opposite door.

RELATED APPLICATION

This application is a continuation of application Ser. No. 10/504,253filed Aug. 10, 2004, which claims priority to PCT Application No.PCT/GB2004/001534 filed Apr. 7, 2004, which claims priority to GB0308002.5 filed Apr. 7, 2003, each of which is hereby fully incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to an aircraft landing gear door assembly.In particular, the invention relates to an aircraft landing gear doorassembly designed to reduce the noise generated by the interaction ofthe landing gear and the air flowing past it during flight, take-offand/or landing.

BACKGROUND OF THE INVENTION

It is desirous to reduce the noise generated by aircraft, for example,to lessen disruption or inconvenience, resulting from aircraft noise,caused to the public on the ground near airports. A significant amountof noise is generated by the interaction of the aircraft and the airflowing past it, which results in turbulent flows and consequentlynoise. It is particularly important to reduce noise created duringapproach of the aircraft on landing. During approach, a significantcontribution to the amount of noise that the aircraft generates is madeby the landing gear, which is typically deployed early for landing forsafety reasons. The deployment of the landing gear increases drag andassists deceleration of the aircraft. During take-off, noise from thelanding gear is a less significant factor because engine noise isgenerally greater and because the landing gear is generally stowed atthe earliest opportunity to reduce drag and aid take-off. During normalflight, the landing gear of an aircraft is typically stowed in a landinggear bay, the bay being closed off by doors so that no part of thelanding gear is subjected to the air flow.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an aircraft landing geardoor assembly that reduces the amount of noise generated by the aircraftduring landing and approach on landing. For example, it is an object ofthe present invention to provide a landing gear door assembly, whereinthe noise generated is less than the noise that would generated if alanding gear door assembly of the same size were used but which has notbeen adapted, designed or manufactured in accordance with the presentinvention.

According to a first aspect of the invention there is provided anaircraft landing gear door assembly including a door, which is moveableto an open position, in which the landing gear can be deployed throughan aperture, and moveable to a closed position, in which the door isclosed across the aperture, wherein at least a part of the door isarranged for movement of a first type, in which the door moves betweenthe closed position and the open position, wherein at least a portion ofthe door is also arranged for movement of a second type, in which saidat least a portion of the door moves to a position in which said atleast a portion of the door acts as a fairing to reduce the noise causedby the landing gear or a part thereof when the landing gear is in itsfully deployed position, and wherein the first type of movement isdifferent from the second type of movement.

By providing a door, or a portion thereof, that is able to be speciallymoved into a fairing position (by means of the second type of movement),it is possible to use the door to divert the airflow away from thelanding gear in a more effective manner than hitherto possible, therebyreducing the amount of noise generated by the interaction of the airflowwith the landing gear. Whilst prior art landing gear door assemblieshave been proposed, where a door may be left in a half open positionacting as a ramp type fairing, thereby diverting airflow away from partsof the landing gear, such proposals have not allowed the movement of thedoor to be of a type different from that used to move the door betweenits open and closed positions. Furthermore, such proposals have not beenmade with the aim of noise reduction in mind. Also, the ability of thedoor (of that prior art proposal) to act as a noise reducing fairingwould in any case be restricted because the door is arranged for onlyrotational movement about a fixed axis.

The first type of movement is preferably rotational movement and,preferably about an axis, that in use, is substantially parallel to thelength of the aircraft.

The first type of movement is preferably rotational movement about anaxis disposed at a location adjacent to a longitudinal edge of theaperture.

Preferably the second type of movement is rotational movement. The firstand second types of movement may both be rotational movement, the typesof movement being different in that the axes of rotation do notcoincide. The second type of movement is preferably rotational movementabout an axis, that in use, is substantially transverse to the length ofthe aircraft.

The second type of movement may be rotational movement about an axis,that in use, is substantially parallel to the door when in the closedposition. Preferably, the door, or a portion thereof, is rotated aboutan axis that is substantially horizontal and perpendicular to thelongitudinal length of the aircraft to move it to the fairing position.

There is provided, according to a second particularly advantageousaspect of the invention, an aircraft landing gear door assemblyincluding a door, which is moveable to an open position, in which thelanding gear can be deployed through an aperture, and moveable to aclosed position, in which the door is closed across the aperture,wherein the door is rotatable (which may be equivalent for example tothe first type of movement mentioned above) about an axis substantiallyparallel to the length of the aircraft to move the door between theclosed position and the open position, wherein at least a portion of thedoor is also rotatable (which may be equivalent for example to thesecond type of movement mentioned above) about an axis, which is bothtransverse to the length of the aircraft and substantially parallel tothe door in its closed position, to move said at least a portion of thedoor to a position in which it acts as a fairing to reduce the noisecaused by the landing gear or a part thereof. In this second aspect ofthe invention, the second type of movement is preferably rotationalmovement about an axis disposed at a location adjacent to a foretransverse edge of the aperture. In this aspect, said portion of thedoor in its fairing position may act as a ramp type fairing.

All parts of the door may be arranged for movement of the first type.

The second type of movement may be rotational movement about an axis,that in use (for example when the door is in the fairing position), issubstantially transverse to the door when in the closed position. Thesecond type of movement may be rotational movement about an axis alignedwith a part of the surface of the door. At least a part of the door maybe rotated about an axis that is substantially vertical to move it tothe fairing position. At least a part of the door may be rotated about amoveable axis, the axis moving for example with the door when the dooris moved between the open and closed positions. Preferably, the secondtype of movement is rotational movement about an axis that in use issubstantially parallel to a surface of the door and moves with said atleast part of the door as it moves between the open and closedpositions.

There is provided, according to a third particularly advantageous aspectof the invention, an aircraft landing gear door assembly including adoor, which is moveable to an open position, in which the landing gearcan be deployed through an aperture, and moveable to a closed position,in which the door is closed across the aperture, wherein the door isrotatable (which may be equivalent for example to the first type ofmovement mentioned above) about a first axis substantially parallel tothe door in its closed position to move the door between the closedposition and the open position, wherein at least a portion of the dooris also rotatable (which may be equivalent for example to the secondtype of movement mentioned above) about a second axis to move said atleast a portion of the door to a position in which it acts as a fairingto reduce the noise caused by the landing gear or a part thereof,wherein the second axis is, when the door is in its open position,transverse to the door in its closed position.

The first and/or second types of movement are preferably rotationalmovement about a fixed axis. Whilst it is possible for a door to bemounted such that its movement is a complex combination of translationaland rotational movements, fixed-axis rotation provides a simple andreliable design.

The door assembly may be so arranged that the first and second types ofmovement are effected simultaneously for at least part of the respectivemovements. For example, said at least a part of the door may begin themovement of the first type (movement between the closed and openpositions) and then, before completion of the first type of movement,said at least a portion of the door may begin the movement of the secondtype (movement into a fairing position). Said at least a part of thedoor that moves with the first type of movement may of course comprisesaid at least a portion of the door that moves with the second type ofmovement and vice versa.

Said at least a portion of the door that moves with the second type ofmovement may move into a position in which it acts as a fairingsimultaneously with said at least a part of the door moving between aclosed and an open position. However, it is preferred that the start ofthe movement of the second type is delayed until said at least part ofthe door has traveled beyond 50% of the distance from the closedposition to the fully open position, and more preferably beyond 75% ofthe distance. By starting the movement of the second type later, thedoor assembly may be able to be configured such that the door assemblymay still readily be opened by back-up means in the event of failure ofany actuation means that may be provided as the primary means foreffecting movement of the door(s) of the door assembly. For example, theconfiguration of the door assembly may be such that moving a portion ofthe door with the second type of movement prematurely (significantlybefore the door is fully open) would give rise to aerodynamic loadswhich would resist movement of the door assembly to its fully openposition.

The door preferably comprises a first section and a second section. Thefirst section may be coupled, preferably hinged, to the second section.Preferably, the axes of rotation of the first and second sections of thedoor for the first type of movement are substantially coincident.Preferably, said at least a portion of the door is the first doorsection. Said at least a part of the door may be the second doorsection. Where only a section of the door is rotated into the fairingposition, simpler and less expensive mounting and actuating arrangementscan be used. Additionally, in certain instances it is advantageous tohave a fairing that has a smaller area than the area of the whole door.

The assembly further may comprise a panel section. The panel section ispreferably coupled to the door. Preferably a hinge is used to couple thepanel section to the door. Said at least a portion of the door maycomprise the panel section. Said at least a portion of the door may bein the form of the panel section. Alternatively, the panel section mayform no part of the door (in that the panel section is not required toclose the aperture that the door closes over). The panel section ispreferably rotatable relative to at least a part of the door formovement of the second type. In an especially advantageous embodiment,the panel section can be coupled to a door section. In this instance,the panel section, together with the door section, can be positioned toact as fairings, for example to provide a V-shaped fairing where thepoint of the V is positioned in front of the landing gear. In use, thepoint of the V-shaped fairing thereby formed may split the air flowingonto the door section and the panel section, when the door assembly isin the fairing position.

The door is preferably coupled to the aircraft using a couplingmechanism, wherein the coupling mechanism allows movement of the firsttype and of the second type. The door may be coupled to the aircraftlanding gear bay, the aircraft landing gear or other suitable areas ofthe aircraft.

The coupling mechanism may include two linkages, a first for linking thedoor to the aircraft for movement of the first type and a second forlinking the door to the aircraft for movement of the second type. Theassembly may be arranged such that, in use, during movement of the firsttype the door is coupled to the first linkage and decoupled from thesecond linkage and during movement of the second type the door isdecoupled from the first linkage and coupled to the second linkage. Sucha feature may be advantageous, especially in relation to the secondaspect of the invention. Means, for example electronic means or amechanical mechanism, may be provided to prevent the door from beingsimultaneously decoupled from the first linkage and decoupled from thesecond linkage.

The coupling mechanism may comprise a rotatable frame. For example, thedoor may be coupled to the aircraft using a coupling mechanism thatincludes a rotatable frame, wherein the door is attached to androtatable about the frame for movement of one of the first and secondtypes, and the frame is attached to and rotatable about the aircraft formovement of the other of the first and second types.

Preferably, the door is attached to and rotatable about the frame formovement of the first type, and the frame is attached to and rotatableabout the aircraft for movement of the second type. Thus, the frame maybe able to contribute to the fairing effect. In that case, the frame isadvantageously open on one side, for example so that the frame does notneed to be moved to allow the landing gear to be moved from its storedposition (when the landing gear is, for example, wholly contained withinthe interior of the aircraft, for example within a landing gear bay) toits operative position (the position of the landing gear when ready forlanding).

In the fairing position, said at least a portion of the door ispreferably positioned to divert air away from at least a portion of thelanding gear. Advantageously, said at least a portion of the door ispositioned to divert air away from noise generating parts of the landinggear, for example, steering actuators (comprising rods, linkages, andthe like), brake actuators and drag stays. Said at least a portion ofthe door may be positioned to divert air away from further doors of thedoor assembly.

Said at least a portion of the door may be positioned to divert air in asubstantially downwards direction. Said at least a portion of the doormay be positioned to divert air in a substantially horizontal direction.Said at least a portion of the door may be positioned to divert air in adownwards and horizontal direction. Preferably, the door assembly is soarranged that when in the fairing position the door assembly splits theairflow. For example, said at least a portion of the door may bepositioned to split the airflow, diverting a first portion of theairflow in a first direction and a second portion of the airflow in asecond direction. One door or part thereof (possibly including one ormore panels coupled thereto) may form at least part of a V-shapedfairing which so splits the airflow. Alternatively, two separateindependent panels, doors, or portions of doors, or panels attached tothe same, may meet to form a V-shaped fairing which so splits theairflow. For example, an independent door, or portion of a door, orpanel attached to the same, may meet a panel that is not part of a door,such as a fairing panel to form a V-shaped fairing which so splits theairflow.

The door assembly preferably further comprises a second door, the seconddoor being movable between open and closed positions, the second doorbeing adjacent to the first door in the open and closed positions. Thesecond door is preferably arranged for movement of the first type tomove the second door between the closed and open positions. The fixedaxes of rotation of the first and second doors for the first type ofmovement are preferably substantially coincident. Preferably, the firstand second doors are arranged so that they may be arranged to move as asingle unit. The first and second doors may be able to be coupled bymeans of a breakable coupling. The landing gear and the door assemblymay be so configured that when the landing gear is fully deployed only asmall area of the aperture is filled with the landing gear. The seconddoor may at least partially cover this area when in the closed position.The second door may, for example, be what is commonly referred to as the‘hinge door’, for example, of a main landing gear door assembly. Thesecond door may be arranged so that it does not perform the function ofa noise-reduction fairing. The first and second doors may be so arrangedthat when the first door, or a portion thereof, is in the fairingposition it diverts air away from the second door.

It is possible to provide respective drives, for example, linearactuators, for each door but it is also possible to provide a drive forthe first door only and to move the second door by coupling it to thefirst door. Thus the first and second doors may be arranged to becoupled to move as a single unit between their open and closedpositions, and be decoupled to enable the first door to moveindependently of the second door between the open position and thefairing position of the first door. Such an arrangement is especiallypreferred in relation to the second aspect of the invention.

In a conventional door assembly it is common for a pair of doors to beprovided. The door assembly may further comprise a third door that ismovable between open and closed positions. The first and third doors mayform a pair of doors. The third door may be adjacent to the first doorin the closed position. The first and third doors may define a pair ofdoors on opposite sides of the aperture. The third door is preferablyarranged for movement of a third type, similarly or identical to thefirst type, to move the third door between the closed and openpositions. The fixed axes of rotation of the first and third doors forthe first and third types of movement are preferably substantiallyparallel. The third door may be movable to and from a fairing position.The third door may be arranged for movement of a fourth type, similar oridentical to the second type, to move the third door to the fairingposition. The axes of rotation of the first and third doors for thesecond and fourth types of movement may be substantially coincident,especially when the axis is parallel to the door in the closed positionand transverse to the length of the aircraft. In such a case, the firstand third doors may be arranged so that they may be moved as a singleunit during movement of the second and fourth types, respectively. Suchan arrangement is particularly suited to the second aspect of theinvention. The axes of rotation of the first and third doors for thesecond and fourth types of movement may be substantially parallel andspaced apart, especially when the axes are transverse to the doors inthe closed position. Such an arrangement is particularly suited to thethird aspect of the invention.

It will be understood that, because the first and third doors are apair, the third door may include any or substantially all of thefeatures of the first door.

It will be understood that the words “first”, “second” and “third”, whenused in relation to doors, are being used herein merely for ease ofdistinguishing between doors having different features. Therefore,whilst reference is made to second and third doors, it should beunderstood that it is within the scope of the invention to provide adoor assembly including the third door, but not the second door, andvice versa.

The assembly preferably includes locking devices for locking some or allof the doors in their closed, open and/or fairing positions.

Reference is made herein to the doors, axes or other things beingtransverse to other doors, axes or other things. It will be understoodthat whilst the word “transverse” is used to cover preferredarrangements where the angle in question is about 90 degrees (say,between 75 and 105 degrees), the term transverse is also used to coverangles that might not be considered as strictly being perpendicular. Forexample, the term transverse may cover angles ranging from 50 degrees to130 degrees. Similarly, the word “parallel” and the term “substantiallyparallel” may cover angles significantly different from 0 degrees. Forexample, an axis may be considered as being substantially parallel to asurface (which need not necessarily be flat) provided that the angle ofseparation is less than 30 degrees.

The landing gear door assemblies described herein may be associated witha nose landing gear, a main landing gear or other type of landing gear.It will be understood that in this context the term main landing gear isa landing gear that sustains a significant share of the loads sustainedby the landing gear of the aircraft during landing and would normallyfor that reason exclude the nose landing gear.

The invention also provides an aircraft including a landing gear doorassembly according to the invention described herein.

According to the invention there is also provided a method of reducingnoise caused by landing gear on an aircraft including a step ofmanufacturing a landing gear door assembly according to the inventiondescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example certain embodiments of the invention will now bedescribed with reference to the accompanying schematic drawings, ofwhich:

FIG. 1 is a perspective view from below, according to a first embodimentof the invention, of a portion of an aircraft nose landing gear doorassembly with the doors shown all being closed,

FIG. 2 is a perspective view from below, according to the firstembodiment of the invention, of a portion of an aircraft nose landinggear door assembly with the landing gear deployed and all the doorsopen,

FIG. 3 is a perspective view from below, according to the firstembodiment of the invention, of a portion of an aircraft nose landinggear door assembly with the landing gear deployed, the fore doors closedand the aft doors open,

FIG. 4 is a perspective view from below, according to the firstembodiment of the invention, of a portion of an aircraft nose landinggear door assembly with the landing gear deployed, the fore doorspositioned to act as fairings and the aft doors open,

FIG. 5 is a perspective view from above, according to the firstembodiment of the invention, of a portion of an aircraft nose landinggear door assembly showing the mounting arrangements for the doors,

FIG. 6 is a perspective view from above, according to a secondembodiment of the invention, of a portion of an aircraft nose landinggear door assembly with an alternative mounting arrangement for thedoors,

FIG. 7 is a perspective view from below, according to a third embodimentof the invention, of a portion of an aircraft nose landing gear doorassembly with all the doors shown closed,

FIG. 8 is a plan view, according to the third embodiment of theinvention, of a portion of an aircraft nose landing gear door assemblyin the open position,

FIG. 9 is a plan view, according to the third embodiment of theinvention, of a portion of an aircraft nose landing gear door assemblyin a fairing position,

FIG. 10 is a perspective view from below, according to a fourthembodiment of the invention, of a portion of an aircraft nose landinggear door assembly with both doors shown closed,

FIG. 11 is a plan view, according to the fourth embodiment of theinvention, of a portion of an aircraft nose landing gear door assemblyin a faired open position,

FIG. 12 is a plan view, according to a fifth embodiment of theinvention, of a portion of an aircraft main landing gear door assemblyin the closed position,

FIG. 13 is a sectional view, according to a fifth embodiment of theinvention, of a portion of an aircraft main landing gear door assemblyin the open position,

FIG. 14 is a perspective view from the front, according to the fifthembodiment of the invention, of a portion of the main landing gear doorassembly in a faired open position,

FIG. 15 is a perspective view from the front, according to a sixthembodiment of the invention, of a portion of the main landing gear doorassembly in an alternative faired open position,

FIG. 16 is a plan view, according to a seventh embodiment of theinvention, of a portion of an aircraft main landing gear door assemblyin the open position,

FIG. 17 is a plan view, according to the seventh embodiment of theinvention, of a portion of an aircraft main landing gear door assemblyin a faired open position,

FIG. 18 is a perspective view from below, according to an eighthembodiment of the invention, of an aircraft main landing gear doorassembly in a closed position,

FIG. 19 is a sectional view, according to the eighth embodiment of theinvention, of a main landing gear door assembly moving from the closedposition to an open position, the nose landing gear assembly moving froma stowed position,

FIG. 20 is a front sectional view, according to the eighth embodiment ofthe invention, of the main landing gear door assembly in a faired openposition, and

FIG. 21 is a plan view, according to the eighth embodiment of theinvention, of the main landing gear door assembly in the position shownin FIG. 20.

DETAILED DESCRIPTION OF THE DRAWINGS

The doors of the door assemblies of the embodiments described herein aremovable between a closed position, in which the doors are closed acrossan aperture, an open position, in which the doors are open to allowlanding gear to be deployed through an aperture, and a further position,hereinafter described as the fairing position, in which at least a partof one of the doors acts as a fairing to divert airflow from the landinggear or a part thereof and thereby reduce the noise caused byinteraction of the airflow with the landing gear, or a part thereof.

For each embodiment of the invention described, the structure andoperation of the door assembly will be described by referring firstly tothe doors, the axes about which they are arranged to rotate and thepositions they occupy in the open, closed and fairing positions.Thereafter the mountings and linkages that achieve the desired movementswill be described.

FIGS. 1 to 5 illustrate a first ramp type embodiment of the invention asapplied to an aircraft nose landing gear.

The door assembly shown in FIGS. 1 to 5 includes five doors: a firstdoor 1, a second door 2, a third door 3, a fourth door 4 and a fifthdoor 5.

Referring to FIG. 1, the doors 1 to 5 are shown in their closedpositions across an aperture 6 in an aircraft skin 7. The direction offlow of air relative to the door assembly is indicated by arrow A whichpoints to the right in FIG. 1, since the aircraft is moving to the left.

It may be seen that the first door 1 and third door 3 are substantiallyrectangular in shape but that each has a smaller rectangular shapedsection missing from one corner. The first door 1 is bounded by outer 1a and inner 1 b longitudinal edges and fore 1 c and aft 1 d transverseedges. The cut out section of the first door 1 is missing from thecorner that would have been formed by the longitudinal inner edge 1 band the transverse aft edge 1 d. The third door 3 is of similar lengthand width to the first door and is bounded by inner 3 a and outer 3 blongitudinal edges and fore 3 c and aft 3 d transverse edges. Again,there is a cut out section of the third door, the cut out being at thecorner that would have been formed by the longitudinal inner edge 3 aand the transverse aft edge 3 d. The fifth door 5 is substantiallyrectangular in shape and lies within the space formed by the two cut outsections. The second 2 and fourth 4 doors are rectangular in shape andare of much shorter length than the doors 1 and 3 and are of a narrowerwidth. They are each bounded by outer and inner longitudinal edges, 2 a,4 b, 2 b, 4 a respectively, and fore and aft edges, 2 c, 4 c, 2 d, 4 drespectively.

The first door 1 is mounted for fixed-axis rotation about a firstlongitudinal axis, disposed at a position adjacent to a firstlongitudinal edge of the aperture 6 and parallel to the longitudinallength of the aircraft, and for fixed-axis rotation about a transverseaxis, disposed at a position adjacent to the fore transverse edge of theaperture 6. The second 2 door is mounted with only one degree offreedom. The second door 2 is mounted for fixed-axis rotation only abouta second longitudinal axis that is parallel to, but spaced inwardly of,the first longitudinal axis. The third and fourth doors 3, 4 are mountedfor movement in a symmetrical manner to the first and second doors 1, 2.Thus, the third door 3 is mounted for fixed-axis rotation about a thirdlongitudinal axis, disposed at a position adjacent to a secondlongitudinal edge (on the opposite side of the aperture to the firstlongitudinal edge) of the aperture and parallel to the longitudinallength of the aircraft and, about the transverse axis (the sametransverse axis as mentioned above in relation to the first door). Also,the fourth door 4 is mounted only for fixed-axis rotation about a fourthlongitudinal axis parallel to, but spaced inwardly of, the secondlongitudinal axis.

In the embodiment described herein the first door 1 is arranged torotate about only one axis at a time. Similarly, the third door 3 isarranged to rotate about only one axis at a time. Thus, the doors 1 and3 are able to rotate from their closed positions of FIG. 1 either totheir open positions of FIG. 2 by rotating about their respectivelongitudinal axes of rotation or to their fairing position of FIG. 4 byrotating about the transverse axis.

The fifth door 5 is fixed to the landing gear (not shown) and thereforerotates about the same axis as the landing gear.

In the closed position, as shown in FIG. 1, the doors 1 to 5 arepositioned across and cover the generally oblong shaped aperture 6 inthe aircraft skin 7. The inner side edges 1 b and 2 b of the first andsecond doors lie immediately adjacent to the inner side edges 3 a and 4a of the third and fourth doors and the transverse aft edges 1 d and 3 dof the first and third doors lie immediately adjacent to the transversefore edges 2 c and 4 c of the second and fourth doors. The fifth door 5lies within the space formed by the two missing corner sections of thefirst and third doors. The aft transverse edge 5 d of the fifth doorlies immediately adjacent to a portion of the fore transverse edge 2 cof the second door and to a portion of the fore transverse edge 4 c ofthe fourth door.

Referring to FIG. 2, the door assembly is shown in its open positionwith the nose landing gear 10 in its deployed position. The nose landinggear 10 includes wheels 11, a central support column 12 (or leg) and adrag stay 13. The doors 1 to 4 are positioned with their outerlongitudinal edges la, 2 a, 3 b, and 4 b parallel and adjacent to thelongitudinal edges of the aperture and with their transverse fore andaft edges 1 c, 1 d, 2 c, 2 d, 3 c, 3 d, 4 c, 4 d extending substantiallydownwards from the aircraft. The fifth door 5 (hidden from view in FIG.2) is fixed to the landing gear and therefore moves with the landinggear 10 to a substantially vertical position.

Between the open and fairing positions, the door assembly moves througha semi-closed position as shown in FIG. 3. In this position, the landinggear 10 is in its fully deployed position, the first and third doors 1,3 are in their closed positions and the second and fourth doors 2, 4 arein their open positions.

In the fairing position, as shown in FIG. 4, the doors 1 and 3 act as‘ramp’ type fairings extending from the fore edge of the aperture 6, ina direction both downwards and towards the landing gear 10. The doors 1and 3 are positioned with their inner longitudinal edges 1 b and 3 alying adjacent to each other and with their transverse fore edges 1 cand 3 c parallel and adjacent to the fore transverse edge of theaperture 6. The longitudinal edges 1 a, 1 b, 3 a and 3 b extenddiagonally downwards. When in the fairing position, the angle alpha. ofseparation between the longitudinal edges of the aperture and thelongitudinal edges of the doors 1 and 3 is normally in the range of 10degrees to 45 degrees. The particular position to which the doors 1 and3 are moved depends on many factors, for example, the extent to whichthe landing gear may be shielded by the doors, and can be controlled byan operator of the aircraft. In the fairing position the doors 2 and 4remain in their open positions, namely, with their longitudinal edges 2a, and 4 b parallel and adjacent to the longitudinal edges of theaperture and with their transverse edges 2 c, 2 d, 4 c and 4 d extendingsubstantially downwards from the aircraft. As the fore doors 1 and 3 arewider than the aft doors 2 and 4, when in the faired open position thefirst and third doors 1 and 3 shield the second and fourth doors 2 and 4(see FIG. 1 for example). The fifth door 5 remains in its open positionwhen the first and third doors 1, 3 are in the faired open position.

Having now described the doors, the axes about which they rotate and thepositions that they adopt in the closed, open and fairing positions, thedetails concerning the mounting of the doors will be described.

Referring to FIG. 5, the first and third doors 1, 3 each have twotransverse crank arms 14, each arranged to be couplable to, anddecouplable from, the inside face of the door, the crank arms 14 beingpositioned at equispaced intervals along and adjacent to the transversefore edges 1 c, 3 c of the doors. The opposite ends of the crank arms 14are rotatably connected to a mounting (not shown) which is fixed to theaircraft structure 7 (only partially shown) inside the landing gear bay.The transverse crank arms 14 are connected such that they are rotatableabout an axis parallel to the transverse edge of the aperture.

The first and third doors are also each provided with two longitudinalcrank arms 15, each arranged to be couplable to, and decouplable from,the inside face of the door, at spaced apart positions adjacent to theouter longitudinal edge 1 a, 3 a of each door 1, 3, respectively. Theopposite ends of the crank arms 15 are rotatably connected to a mounting(not shown) which is fixed to the aircraft structure 7 (only partiallyshown) inside the landing gear bay. The longitudinal crank arms 15 ofeach door are connected such that each door is rotatable about an axisparallel and adjacent to the longitudinal edge of the nearest side ofthe aperture 6 (the first and third longitudinal axes mentioned above).

Thus by coupling transverse crank arms 14 and decoupling longitudinalcrank arms 15, the doors 1 and 3 can be rotated about an axis parallelto the transverse edge of the aperture 6, and by coupling longitudinalcrank arms 15 and decoupling transverse crank arms 14, the doors 1 and 3can be rotated about their respective longitudinal axis of rotation.

The second door 2 has two longitudinal crank arms 16, which at one endare each fixed to the inside face of the door at spaced-apart positionsadjacent to the door's outer longitudinal edge 2 a, and at their otherends are rotatably connected, by means of a connection (not shown), to amounting (also not shown) which is fixed to the aircraft structure 7inside the landing gear bay. The rotatable connections (not shown)enable the second door 2 to rotate about the second longitudinal axis(parallel and adjacent to the first longitudinal axis about which thefirst door 1 is able to rotate).

The fourth door 4 is mounted in a similar manner to that of the seconddoor 2. Thus, the fourth door 4 is mounted for rotation about the fourthlongitudinal axis, parallel and adjacent to the second longitudinal edgeof the aperture 6 (parallel and adjacent to the second longitudinal axisabout which the second door 2 is able to rotate), by means of twolongitudinal crank arms 16 fixed to the inside face of the door androtatably connected at connections (not shown) to the aircraft structure7.

Thus the doors 2 and 4 can each be rotated about their respective axesparallel to the longitudinal edges of the aperture.

The fifth door 5 is fixed to the landing gear assembly 10 and istherefore mounted for rotation with the landing gear 10 about agenerally transverse axis.

During normal usage it is not possible for a door to be simultaneouslydecoupled from all of the crank arms 14, 15, 16.

The movement of the doors 1, 2, 3, 4, 5 from their closed positions totheir open positions is effected by one linkage connected to all thedoors so that their movement is simultaneous. The movement of the firstand third doors 1 and 3 from their open positions to their fairingpositions is also effected by one linkage connected to both doors sothat their movement is simultaneous.

Hydraulic actuators are provided for controlling movement of the doors,for controlling the locking of the first and third doors 1 and 3 intheir fairing positions and, for controlling the locking of the secondand fourth doors 2 and 4 in their open positions.

As the skilled person will appreciate, there are various linkage andactuator arrangements that could be used to offer the same result.

The operation of the doors will now be described with reference to FIGS.1 to 4.

During normal flight, the doors 1 to 5 are in their closed position asshown in FIG. 1, with the landing gear stowed in the landing gear bay.

During approach of the aircraft when landing, the first to fourth doors1 to 4 are opened by rotating them through 90 degrees about theirlongitudinal axes (the axes being parallel to the longitudinal edges ofthe aperture 6) to the position shown in FIG. 2. As the landing gear 10deploys, the fifth door 5 moves with the landing gear (and thereforemoves from its closed position to its open position) and the first tofourth doors 1 to 4 move from their closed positions towards their openpositions, thereby revealing the whole of the aperture 6 open andallowing the landing gear to pass through it. When the landing gear 10is fully deployed, only a small area of the aperture 6 is filled withthe landing gear (an area that in the closed position would be coveredby the second, fourth and fifth doors 2, 4). The second and fourth doors2, 4 would, if otherwise able to do so, be unable to move from the openposition to the closed position because their movement would beobstructed by the deployed landing gear 10.

Once the landing gear 10 has been deployed, the landing gear 10 andsecond and fourth doors 2, 4 are locked in position. The first and thirddoors 1, 3 are then rotated back through 90 degrees into the closedposition (as shown in FIG. 3) about the first and third longitudinalaxes, respectively. Then, while in the closed position, the first andthird doors 1, 3 are coupled to the transverse crank arms 14 and thende-coupled from the longitudinal crank arms 15. The first and thirddoors 1, 3 are then moved, together as a unit, into the fairing positionby rotating them by 30 degrees about the axis parallel to the transversefore edge of the aperture 6 into the position shown in FIG. 4.

In this position the first and third doors act as a ‘ramp’ type fairing,diverting the airflow substantially downwards, thereby shielding theupper part of the landing gear 10 and the second and fourth doors 2, 4.The amount of landing gear shielded depends on the angle at which thedoors are positioned to extend from the aircraft skin.

The first and third doors 1 and 3 remain in the fairing positionthroughout approach and landing of the aircraft. On take-off the doors 1and 3 are moved back to their closed position, firstly to reduce dragand secondly because the noise generated during take-off by the enginesis so great that the benefit of reducing noise by means of the ramp typefairing would not be significant. Before take off (while the landinggear is still deployed), the doors 1 and 3 are therefore rotated backthrough 30 degrees returning them to their closed position (to aposition much like that as shown in FIG. 3). While in the closedposition, the first and third doors 1, 3 are coupled to the longitudinalcrank arms 15 and are de-coupled from the transverse crank arms 14. Incontrast, the second and fourth doors 2 and 4 remain open while theaircraft lands and, in due course, takes off again. After take-off whenthe landing gear needs to be stowed again, the first and third doors 1and 3 are rotated through 90 degrees about the first and thirdlongitudinal axes to the position shown in FIG. 2. The landing gear (andattached fifth door 5) are then retracted through the whole of theaperture 6 and, then, the doors 1 to 4 are closed, by simultaneousrotation of the first and second doors 1, 2 and the third and fourthdoors 3, 4 about their respective longitudinal axes of rotation,respectively.

FIG. 6 illustrates a second embodiment similar to the first ‘ramp’ typefairing embodiment described above, but having a different mountingarrangement for moving the doors 1 and 3 between their closed, open andfairing positions.

The door assembly includes the five doors 1, 2, 3, 4, 5 as describedpreviously, but all being of the same width, and a rotatable U-shapedframe 20 to which the doors 1 and 3 are rotatably attached. The frame 20comprises a base 21, a first arm 22 a extending at right angles from oneend of the base 21 and, a second arm 22 b, parallel to the first arm 22a, extending at right angles from the opposite end of the base 21. Theaperture 6 in this second embodiment also has a fore portion that iswider from an aft portion. The size, configuration and operations of thesecond, fourth and fifth doors 2, 4, 5 are substantially the same asthat described above with reference to the first embodiment.

The frame 20 in its closed position covers a part of the aperture 6 andits outside surface is flush with the exterior of the aircraft. Theframe 20 is rotatably mounted on transverse crank arms 23 for fixed-axisrotation about an axis parallel and adjacent to the transverse fore edgeof the aperture 6. Each of the transverse crank arms 23 is at one endconnected to the inside face of the base 21 of the frame 20 at spacedapart positions and is at the other end rotatably mounted at aconnection 24 to the aircraft structure 7 inside the landing gear bay.The rotatable connections 24 all lie on an axis of rotation parallel andadjacent to the transverse fore edge of the aperture 6.

In a manner similar to that described above with reference to the firstembodiment, the first door 1 is mounted for rotation, about an axisparallel to the longitudinal edge of the aperture 6, by means oflongitudinal crank arms (not shown) each fixed at one end to the doorand rotatably mounted at the other end to the first arm 22 a of theframe 20. The third door 3 is similarly rotatably mounted to the secondarm 22 b of the frame 20 for fixed axis rotation about a parallel axis.Thus by rotating the doors 1 and 3 downwards about their longitudinalaxes of rotation whilst holding the frame 20 in its closed position, thefirst and third doors 1, 3 can be moved from their closed positions,shown in FIG. 6, to their open positions (not shown). With the first andthird doors 1, 3 in their closed position, rotation of the frame 20,together with the first and third doors 1, 3 (that move with the frameas a unit), downwards about the transverse axis of rotation moves thedoors 1 and 3 and the surrounding frame 20 together to form a rampedtype fairing.

FIGS. 7 to 9 illustrate a third V-shaped fairing embodiment of theinvention as applied to an aircraft nose landing gear. The nose landinggear door assembly shown in FIGS. 7 to 9 includes five doors: a firstdoor 31, a second door 32, a third door 33, a fourth door 34 and a fifthdoor 35.

The second door 32, fourth door 34 and fifth door 35 of this embodimentcorrespond to the second 2, fourth 4 and fifth 5 doors describedpreviously in relation to the first and second embodiments and operatein the same way as described above. The first and third doors 31, 33 areshaped identically to the first and third doors as described above withreference to the first and second embodiments, and move between theiropen and closed positions in a similar manner, but move to a differentfairing position and by means of a different mechanism, thesedifferences being described in further detail below.

Thus the first door 31 is substantially rectangular in shape and isbounded by outer 31 a and inner 31 b longitudinal edges and by fore 31 cand aft 31 d transverse edges and similarly the third door 33 is boundedby longitudinal inner and outer edges 33 a and 33 b and by fore and aftedges 33 c and 33 d. Also, the first and third doors 31, 33 are eachmounted for fixed-axis rotation about first and second longitudinalaxes, disposed at a location adjacent to the opposite longitudinal edgesof the aperture 6, respectively. The first and third doors 31, 33 arehowever also mounted for rotation about respective axes that aresubstantially vertical, when the doors are in the open position.

In the closed position, as shown in FIG. 7, the doors 31 to 35 arepositioned across and cover the rectangular shaped aperture 6 in theaircraft skin 7. FIG. 8 shows a schematic plan view of the door assemblyin its open position and with the nose landing gear 10 in its deployedposition. The nose landing gear 10 includes wheels 11 (not shown in FIG.8), a central support column 12 (or leg) and a drag stay 13 (not shownin FIG. 8). The relative arrangements of the doors in their open andclosed positions are as described with reference to the firstembodiment.

FIG. 9 shows a schematic plan view of the door assembly with the firstand third doors 31, 33 in the fairing position, in which the first 31and third 33 doors are positioned to divert the airflow away from anupper portion of the landing gear. The first door 31 is positioned withits transverse edges 31 c and 31 d extending substantially downwardsfrom the aircraft and with its longitudinal edges 31 a and 31 bextending (as viewed from above) diagonally in the direction from themid point of the fore transverse edge of the aperture 6 to a point onthe first longitudinal edge of the aperture 6 (the edge nearest thefirst door 31). The third door 33 mirrors the position of the first door31, so that its transverse edges 32 c and 32 d extending substantiallydownwards from the aircraft and its longitudinal edges 32 a and 32 bextend diagonally from the mid point of the fore transverse edge of theaperture to a point on the second longitudinal edge of the aperture (theedge nearest the second door 31). Thus, the first and third doors 31, 33form a V-shaped fairing (as viewed from above) in front of the landinggear 10. The second, fourth and fifth doors 32, 34, 35 remain in theiropen positions.

The mechanisms provided to effect the movement of the second, fourth andfifth doors 32, 34, 35 are identical to the mechanisms described abovewith reference to the first embodiment. The mechanisms provided toeffect the movement of the first and third doors 1, 3, are of coursedifferent. In this embodiment, the first door 31 is mounted forlongitudinal rotation about a single arm mounted at one end on theaircraft structure on a rotatable connection having its axis of rotationparallel and adjacent to the longitudinal edge of the side of theaperture 6. The other end of the arm is rotatably mounted on the door,so that the door is rotatable about an axis that is substantiallyparallel to the face of the door and transverse to the longitudinal axisof the aircraft. Thus, when the first door 1 is in its open position,the door 1 is able to rotate about a substantially vertical axis. Thethird door is similarly mounted. Of course, any suitable mechanism forproviding both rotation about a longitudinal axis and rotation about avertical axis when the doors 1, 3, are in their open positions may beprovided.

Thus, the first and third doors 31 and 33 are able to rotate downwardlyfrom the closed positions shown in FIG. 7 through an angle of about 90degrees to the open positions shown in FIG. 8 and then, by causingrotation about a vertical axes of the first and third doors 1, 3relative to the respective crank arms (not shown) that couple the doorsto the aircraft through an angle of about 45 degrees, the first andthird doors 31 and 33 are moved to their fairing positions, as shown inFIG. 9.

Hydraulic actuators are provided for controlling movement of the doors,for controlling movement of the crank arms relative to the doors thatprovide the vertical rotation, and for controlling the locking of thedoors in their open, closed and fairing positions. Also, breakablecouplings are provided between the doors to facilitate movement of thefirst 31 and second 32 doors together as a unit.

During normal flight, the first to fifth doors 31 to 35 are in theirclosed positions (as shown in FIG. 7), with the landing gear stowed inthe landing gear bay and during approach of the aircraft when landing,the first to fifth doors 31 to 35 are opened and the landing geardeploys, in a manner similar to that described above with reference tothe first embodiment. Once the landing gear has been deployed, thelanding gear 10 and the second 32 and fourth doors 34 are locked intoposition. The first and third 31 and 33 doors are then each rotatedabout a respective vertical axis through about 30 degrees into thefairing position (the doors being rotated towards each other). In thefairing position shown in FIG. 9, the fore transverse edge of the firstdoor 31 meets the fore transverse edge of the third door 33 to form apoint, the fairing thereby formed being substantially V-shaped whenviewed from above. Thus, in this position the first and third doors 31and 33 act as a V-shaped fairing, diverting the airflow away from theupper portion of the landing gear, by diverting the air in substantiallyhorizontal directions.

As described above with reference to the first embodiment, the first andsecond doors 31 and 33 remain in the fairing position throughoutapproach and landing of the aircraft, but before take-off they are movedback to their closed position. The second, fourth and fifth doors 2, 4,5 remain in their open positions throughout landing and subsequenttake-off. After take-off, when the landing gear needs to be stowedagain, the first and third doors 31 and 33 are rotated through 90degrees about axes parallel to the longitudinal edge of the aperture tothe position shown in FIG. 8, and the landing gear 10 (and attachedfifth door 5) is then retracted through the whole of the aperture 6 and,whilst the all five doors 31 to 35 move from their open positions totheir closed positions.

FIGS. 10 and 11 illustrate a fourth embodiment of the invention similarto the V-shaped fairing embodiment of FIGS. 7 to 9. The nose landinggear door assembly shown in FIGS. 10 and 11 includes a first and asecond door 36, 37 both of which have two portions.

The first door 36 has a fore portion 36′ (or panel section) and an aftportion 36″. Similarly the second door 37 has a fore portion 37′ (orpanel section) and an aft portion 37″. The first and second doors aresubstantially rectangular in shape and are mounted for fixed-axisrotation about respective first and second longitudinal axes, eachdisposed at a location adjacent to the longitudinal outer edges 36 a and37 b of the doors, respectively.

In the closed position, as shown in FIG. 10, the doors 36 and 37 arepositioned across and cover the rectangular shaped aperture 6 in theaircraft skin 7.

FIG. 11 shows a schematic plan view of the door assembly in the open andfaired position and with the nose landing gear 10 in the deployedposition. The doors 36, 37 have undergone rotation firstly byapproximately 90° about the longitudinal axes so the transverse edges 36c, 37 c extend substantially downwards from the aircraft. Secondly, thefore portions 36′ and 37′ of the first and second doors 36, 37 haverotated to a position in which the airflow A is diverted away from theupper portion of the landing gear 10. The fore portions 36′, 37′ of thefirst and second doors 36, 37 are positioned so that the transverseedges 36 c, 37 c are directly adjacent to each other and positioned inthe region of the mid-line M of the aperture 6. When in the open fairedposition, the fore portions 36′, 37′, when viewed from above, extenddiagonally from the mid-line M of the aperture 6 to the longitudinaledges of the aperture 6 and the aft portions 36″, 37″ of the doors 36,37 extend along the longitudinal edges of the aperture 6 and aresubstantially parallel to each other. The fore portions 36′, 37′ of thefirst and second doors 36, 37 form a V-shaped fairing (as viewed fromabove) in front of the landing gear 10.

The mechanism provided to effect movement of the first and second doors36, 37 from the closed position to the open faired position as shown inFIG. 11 will now be described. The movement of the fore portions 36′,37′ of the doors to the fairing position starts before the aft portions36″, 37″ of the doors reach their fully open position. The doors 36, 37are each mounted for longitudinal rotation about axes parallel andadjacent to the longitudinal edges of the aperture 6 (in a mannersimilar to that described with reference to the first and third doors ofthe first embodiment) by means of arms (not shown) mounted on theaircraft structure 7 and rotatably connected to the aft portions 36″,37″ of the doors 36, 37. The fore portions 36′ and 37′ of the doors arerotatably connected to the aft portions 36″, 37″ about respective hingeaxes 36 h, 37 h. Each hinge axis 36 h, 37 h is substantially parallel tothe face of the door and is transverse to the longitudinal edges 36 a,37 b of the doors 36, 37. Thus there is provided (i) a mechanism toeffect a first type of movement (rotational movement about longitudinalaxes) to move aft portions 36″ and 37″ of the doors 36, 37 into an openposition and (ii) a mechanism to effect a second type of movement(rotation about the transverse hinge axes 36 h, 37 h) to move the foreportions 36′, 37′ into a fairing position. A mechanism is provided toeffect rotation about the hinge 36 h, 37 h axes, during, but onlytowards the end of the movement of, the aft door portions 36″, 37″ fromthe closed position to the fully open position, to bring the foreportions 36′, 37′ of the doors 36, 37 into the fairing position asillustrated in FIG. 11. Thus, the doors 36, 37 proceed from the closedposition shown in FIG. 10 directly to the fairing position shown in FIG.11 without passing via an unfaired, but fully open position. Also, eachfore portion 36′, 37′ of the doors 36, 37 may be considered as beingmoved in both a first and a second type of movement simultaneously.

FIGS. 12, 13 and 14 illustrate a fifth embodiment of the invention asapplied to a main landing gear.

The main landing gear door assembly shown in FIGS. 12 to 14 includesthree doors: a main door 41, a leg door 42 and a hinge door 43. Thelanding gear 47 includes wheels 48, a central support column 49 (or leg)and a drag stay 50.

Referring first to FIG. 12, the doors 41, 42 and 43 are shown in theirclosed positions across an aperture 44. The aperture 44 extends acrossthe fuselage 45 and the wing 46 and is of a size to allow the mainlanding gear 47 to move from its retracted position to its deployedposition. The aperture 44 comprises a fuselage portion and a wingportion. When the landing gear assembly is in its retracted position,the wheels 48 and a small portion of the leg 49 are positioned insidethe fuselage while the drag stay 50 and the remaining portion of the leg49 are positioned inside the wing 46. The fuselage portion of theaperture is therefore wider than the wing portion to allow the landinggear 47 to deploy.

The direction of flow of air relative to the door assembly is indicatedby arrow A which points downwards in FIG. 12, since the aircraft ismoving upwards.

The main door 41 is of the same curvature as the fuselage and is boundedby an inner substantially straight edge 41 a, an outer substantiallystraight edge 41 b, a curved fore edge 41 c and a curved aft edge 41 d.The leg door 42 is substantially rectangular in shape and is bounded byan inner edge 42 a, an outer edge 42 b, a fore edge 42 c and an aft edge42 d. The hinge door 43 is substantially rectangular in shape and isbounded by an inner edge 43 a, an outer edge 43 b, a fore edge 43 c andan aft edge 43 d. The inner edge of the hinge door 43 a is ofsubstantially the same length as the outer edge of the leg door 42 b.

The main door 41 is mounted for fixed-axis rotation about a firstlongitudinal axis that is parallel to the longitudinal length of theaircraft and is disposed at a position adjacent to the longitudinal edgeof the fuselage portion of the aperture 44. The leg door 42 is rotatablymounted on the leg 49 for rotation about an axis parallel to thelongitudinal length of the leg 49. The leg door 42 may therefore berotated about the leg axis to move the leg door to a fairing position asdescribed in further detail below. The leg door 42, being mounted on theleg 49, also rotates with the leg 49 as it deploys by rotating about asecond longitudinal axis. The hinge door 43 is mounted for fixed-axisrotation about a third longitudinal axis. The third axis is disposed ata position adjacent to the longitudinal outer edge of the wing portionof the aperture 44 and is also parallel to the longitudinal length ofthe aircraft. The hinge door 43 is so arranged that it does not undulyobstruct the rotation of the leg door 42 about the axis parallel to thelongitudinal length of the leg 49.

In the closed position, as shown in FIG. 12, the doors 41 to 43 arepositioned across and cover the aperture 44 in the aircraft fuselage 45and wing 46. The main door 41 lies with its inner edge 41 a immediatelyadjacent to the longitudinal edge of the fuselage portion of theaperture 44 and with a portion of its outer straight edge immediatelyadjacent to the inner edge 42 a of the leg door. The outer edge 42 b ofthe leg door lies immediately adjacent to the inner edge 43 a of thehinge door. The hinge door 43 lies with its outer edge 43 b immediatelyadjacent to the longitudinal edge of the wing portion of the aperture44.

Referring to FIG. 13, the main landing gear 47 is shown in its deployedposition. The main door 41, although required to be open duringdeployment of the landing gear 47, is closed once the gear 47 isdeployed. The leg door 42 is fixed to the landing gear 47 and moves withthe gear 47. Thus, the leg door 42 is positioned with its inner andouter edges 42 a, 42 b parallel to the longitudinal length of theaircraft and with its transverse fore and aft edges 42 c, 42 d extendingsubstantially downwards parallel to the leg 49. The hinge door 43 ispositioned with its inner and outer edges 43 a, 43 b parallel to thelongitudinal length of the aircraft and with its transverse fore and aftedges 43 c, 43 d extending substantially downwards from the aircraft.

In the fairing position, as shown in FIG. 14, the leg door 42 has beenrotated about the leg axis so that it is in a plane at an acute angle tothe longitudinal axis of the aircraft. The whole leg door 42 thus actsas a fairing, diverting the airflow in a substantially horizontaldirection away from noise generating parts of the upper portion of themain landing gear assembly 47. The leg door 42 is positioned with itsfore and aft edges extending substantially downwards. The fore edge ispositioned closer to the fuselage than the aft edge. Thus, the inner andouter edges 42 a, 42 b extend diagonally in front of the landing gearleg 49. An angle β of separation is formed between the inner and outeredges 42 a, 42 b of the aperture 44 and an axis parallel to thelongitudinal length of the aircraft. When in the fairing position, theangle β is normally in the range of 10 degrees to 45 degrees. Theparticular position to which the leg door 42 is moved depends on manyfactors, for example, the extent to which the landing gear is requiredto be shielded by the doors, and can be controlled by an operator of theaircraft.

The main door 41 and hinge door 43 are mounted for movement betweentheir open and closed positions be means of standard mechanisms wellknown in the art using crank arms and the like (not shown). The leg door42 is mounted on, and is rotatable about, the leg 49 of the landing gearassembly 47. The leg door 42 is rotatably mounted on the leg 49 by meansof two spaced apart hinges 51 fixed to the leg 49, and to the insideface of the door 42 at spaced-apart positions along an axissubstantially parallel to the fore and aft edges 42 b and 42 c. Thehinges 51 are positioned roughly in line with the length of the leg 49.The exact position of the line along which the hinges 51 are attacheddepends on the relative positions of the aperture 44 and landing gear47. Thus the main and hinge doors 41 and 43 can be rotated about axesparallel to the longitudinal length of the aircraft while the leg door42, when the leg 49 is in its deployed position, can be rotated about asubstantially vertical axis.

Hydraulic actuators are provided for controlling movement of the doors,for controlling the locking of the main and hinge doors 41 and 43 inopen positions and, for controlling the locking of the leg door 42 inits fairing position. As the skilled person will appreciate, there arevarious actuator arrangements that could be used.

The operation of the doors will now be described with reference to FIGS.12 to 14. During normal flight, the main door 41, leg door 42 and hingedoor 43 are in their closed positions as shown in FIG. 12, with thelanding gear 47 stowed in the fuselage and wing portions of the landinggear bay. During the aircraft's approach on landing, the main door 41 isopened by rotating it through about 60 degrees about an axis parallel,and adjacent to, the inner edge of the fuselage portion of the aperture44 to the position shown in FIG. 13. In addition, the hinge door 43 isopened by rotating it through 90 degrees about an axis parallel, andadjacent to, the outer edge of the wing portion of the aperture 44, tothe position shown in FIG. 13. As the main and hinge doors 41 and 43open, the landing gear 47 also deploys (and therefore bringing with itthe leg door 42), with the whole of the fuselage and wing portions ofthe aperture 44 open to allow the landing gear 47 to pass through theaperture 44. When the landing gear 47 is fully deployed only a smallarea of the aperture 44 is filled with the landing gear 47 (an area thatin the closed position would be covered by the hinge door 43 and aportion of the leg door 42). The hinge door 43 would, if otherwise ableto do so, be unable to move from the open position to the closedposition because its movement would be obstructed by the deployedlanding gear 47.

Once the landing gear 47 has been deployed, the landing gear 47 andhinge door 43 are locked in position. The main door 41 is then rotatedback through 60 degrees to its closed position. While in the openposition, the leg door 42 is moved into the fairing position by rotatingit by about 30 degrees about the axis parallel to the landing gear leg49 into the position shown in FIG. 14. In this position, the leg door 42acts as a fairing by diverting the airflow substantially horizontallyand diagonally (when viewed from above) away from the landing gear 47,thereby shielding the upper part of the landing gear. The amount ofshielding of the landing gear depends of course on many factorsincluding the angle at which the leg door 42 is positioned.

The leg door 42 remains in the fairing position throughout approach andlanding of the aircraft. On take-off the leg door 42 is moved back toits open position to reduce drag and because noise considerations areless important during take-off. Before take off (while the landing gearis still deployed), the leg door 42 is therefore rotated back through 30degrees returning it to its open position, as shown in FIG. 13.

The hinge door 43 remains open while the aircraft lands and, in duecourse, takes off again. After take-off when the landing gear needs tobe stowed again, the main door 41 is opened and the landing gear 47 andattached leg door 42 are then retracted through the whole of theaperture 44 whilst the main and hinge doors 41 and 43 are simultaneouslyclosed in a conventional manner.

FIG. 15 illustrates a sixth embodiment of the invention as applied tothe main landing gear. The sixth embodiment is very similar to the fifthembodiment of the invention, except that in this embodiment, a forwardportion only of the leg door 42 is arranged to act as a fairing. Thedoor assembly includes the main and hinge doors 41 and 43 as describedpreviously and a hinged leg door 60.

The hinged leg door 60 comprises two sections, a rotatable fore section61 and a fixed aft section 62. Referring to FIG. 12, the fore section 61of the leg door 60 is bounded by inner and outer side edges 61 a and 61b, and fore and aft side edges 61 c and 61 d. The aft section 62 of theleg door 60 is of similar width (in the transverse direction) to thefore section 61, but of greater length (in the longitudinal direction)and is bounded by fore and aft longitudinal side edges, and inner andouter side edges. The aft edge of the fore section 61 is hinged to thefore edge of the aft section 62, the aft section 62 being fixedlymounted on the leg 49. Thus, the fore section 61 of the leg door 60 ismounted for fixed-axis rotation about an axis parallel to the landinggear leg 49.

In the open and closed positions, the leg door 60 is arranged insubstantially the same positions as in the fourth embodiment, as shownin FIG. 8, as both sections 61, 62 of the leg door 60 are positionedflat against the landing gear leg 49.

On approach when landing and after the deployment of the landing gearhas started, the fore section 61 of the leg door 60 is caused to rotateto the fairing position shown in FIG. 13, at which position the foresection is at an angle of about 45 degrees to its open position. In thefairing position, the fore section 61 of the leg door 60 is positionedwith its fore and aft edges and extending substantially downwards fromthe aircraft and with its inner and outer edges and extending diagonallyin front of the landing gear assembly 47. The aft section 62 of the legdoor 60 remains in its open position.

Again, suitably arranged hydraulic actuators are provided forcontrolling the movement and the locking of the main door 41, the hingedoor 42 and the fore section of the leg door 61.

FIGS. 16 and 17 illustrate a seventh embodiment of the invention asapplied to the main landing gear. The seventh embodiment is very similarto the fifth and sixth embodiments of the invention, except that in thisembodiment, the leg door is in the form of a hinged leg door 60comprising an additional panel 63.

Thus, the hinged leg door 60 in this embodiment comprises threesections, a fore section 61, an aft section 62 and a panel section 63.FIG. 16 shows schematically a sectional plan view of the leg door 60 andthe leg 49 of the landing gear when the leg door 60 is in its openposition. The aft edge of the panel section 63 is hinged to the foreedge of the fore section 61 and the aft edge of the fore section 61 ishinged to the fore edge of the aft section 62. In a manner similar tothe sixth embodiment, the fore section 61 of the leg door is mounted forrotation about an axis parallel to the landing gear leg 49 when in itsdeployed position and the aft section 62 is fixed to the landing gearleg 49. The panel section of the leg door 63 is also mounted forrotation about an axis parallel to the landing gear leg 49 in itsdeployed position.

In the open and closed positions, the leg door 60 is arranged insubstantially the same positions as in the fourth embodiment, as bothsections 61, 62 of the leg door 60 are positioned flat against thelanding gear leg 49 and aligned with the longitudinal axis of theaircraft. The panel section 63 of the leg door 60 is in the openposition folded back onto the fore section 61, so that in the closedposition the panel section 63 is positioned on the landing gear bay sideof the fore section 61. In the fairing position, as shown in FIG. 17,the fore section 61 and the panel section 63 of the leg door 60 arepositioned to provide a V-shaped fairing positioned in front of thelanding gear. Thus, during deployment the leg door 60 rotates downwardlyfrom the closed position with the landing gear through an angle of about90 degrees to the open position shown in FIG. 16 and then the leg doormoves to a fairing position, wherein the first section 61 is rotatedrelative to the aft section 62 by means of the hinge arrangedtherebetween and the panel section 63 is rotated relative to the foresection 61 by means of the hinge arranged therebetween. The firstsection 61 rotates by an angle of about 50 degrees relative to the aftsection 62 and the panel section 63 rotates by an angle of about 100degrees relative to the fore section 61.

FIGS. 18 to 21 illustrate schematically an eighth embodiment of theinvention, providing a V-shaped fairing on a main landing gear doorassembly. The assembly includes a first door 70 that is substantiallyrectangular in shape and has a fore portion (or panel) 72 and an aftportion 73. The fore and aft portions are connected by a hinge 78 whichfacilitates rotation of the fore portion 72 about an axis transverse tothe longitudinal edge 70 a of the door and generally parallel to thesurface of the door. The assembly also includes other doors illustratedschematically in FIGS. 18 to 21 by further door 74. The assemblyadditionally includes a fixed fairing 71 (mounted on the landing gear 10by means of a connector 75 (shown in FIG. 21). The first door 70 ismounted for fixed axis rotation about a first longitudinal axis disposedat a location adjacent to a longitudinal outer edge 70 a of the door.

In the closed position as shown in FIG. 18, the doors 70, 74 arepositioned across and cover the rectangular shaped aperture 6 in theaircraft skin 7.

FIG. 19 shows a section view of the doors 70, 74 as they begin theirmovement from the closed position to an open position. The first door 70moves in accordance with a first type of movement (being rotationalmovement about the first longitudinal axis). The landing gear 10 isshown beginning its movement from its stowed position. The landing gear10 comprises wheels 11 and a central support column (or leg) 12 (allillustrated highly schematically in the Figures). The fixed fairingpanel 71, moves together with the landing gear 10.

FIGS. 20 and 21 show the door 70 in its open and faired position and thelanding gear 10 in a fully deployed position. As shown in section viewin FIG. 20 the landing gear 10 is in a substantially vertical positionextending down from the aircraft fuselage through the opening 6 in theaircraft skin 7. The first door 70 and fixed fairing 71 extendvertically down from the aircraft skin. The other doors 74 have movedback to the closed position.

FIG. 21 shows the shape of the fairing panel 71 which has a fore portion76, and an aft portion 77 fixed in position relative both to each otherand the landing gear 10. In the deployed position, when looking fromabove, the aft fairing portion 77 extends substantially parallel to thelongitudinal axis of the aircraft and the fore fairing portion 76 of thefairing 71 extends diagonally from the end of the aft portion 77 towardsthe midline M of the landing gear 10. FIG. 21 also illustrates how thefirst door 70 acts as a fairing. The fore portion 72 of the door 70moves in accordance with a second type of movement, wherein it isrotated about the hinge 78 during movement of the door from the closedposition to the fully deployed position. Thus the fore portion 72 of thedoor 70 moves in both a first and a second type of movementsimultaneously. The fore portion 72 of the door 70 and the fore portion76 of the fairing panel 71 form a V-shaped fairing (as viewed fromabove) in front of the landing gear 10 that shields the landing gear 10from the air flow A. As can be seen in FIG. 20, only a relatively smallproportion of the landing gear 10 protrudes below the door 70 andfairing panel 71. In this embodiment, when the landing gear is fullydeployed with the door 70 in the fairing position, the support column 12and other parts (not shown) of the landing gear 10 are eithersubstantially entirely shielded from the airflow A by the door 70 andfairing 71 or are within the fuselage of the aircraft.

Reference is made above to transverse crank arms and to longitudinalcrank arms that allow a door to rotate about a transverse axis and abouta longitudinal axis, respectively. It will be understood that the term“transverse” as used in “transverse crank arms” refers to the axis ofrotation of the door and not to the shape or arrangement of the crankarm. Similarly, the term “longitudinal” as used in “longitudinal crankarms” refers to the axis of rotation, rather than the shape orarrangement of the crank arm.

It will be appreciated that various modifications may be made to theabove-described embodiments of the invention without departing from thespirit of the invention. For example, in those embodiments where thereare distinct closed, open-and-not-faired and open-and-faired positionsfor one or more parts of the door assembly the doors or portions thereofthat act as fairings may be so arranged that the movement from theclosed position to the open position and the movement to the fairingposition occurs simultaneously. Similarly, some doors may be stationeryduring the time when the landing gear moves to its deployed position. Inall embodiments, mechanisms may be provided so that the doors aremovable directly from the closed position to the fairing positionwithout proceeding via the open position with both the first and secondtypes of movement occurring simultaneously. Typically, the doors willmove directly from the closed position to the fairing position duringthe deployment of the landing gear for approach of the aircraft onlanding (when reducing noise is most important). The door assemblies maybe arranged such that during take-off the doors move from the fairingposition to the open position to minimise drag on take-off. Duringtake-off engine noise is at such a level that reducing noise generatedby the landing gear is not as important as minimising drag.

The first, second, third and fourth doors of the door assembly of thefirst embodiment could each be of the same width and thus closing over asubstantially rectangular aperture when in the closed position. As aconsequence, the second and fourth doors when open would be shielded toa slightly lesser extent by the first and third doors when in thefairing position, but movement of the doors could as a result besimplified. For example, breakable linkages could be provided betweenthe doors of this variation on the first embodiment to facilitatemovement of (i) the first and second doors, (ii) third and fourth doors,and (iii) first and third doors together as a unit, the linkages beingbreakable, in the sense that they are able to couple and decouple. Thus,when moving the doors from the closed position to the open position, thefirst and second doors on the one hand and the third and fourth doors onthe other hand are moved together as a unit.

The U-shaped frame of the second embodiment could be rotated togetherwith the first and third doors with the first and third doors in theiropen or partially open, position. For example, the door assembly of thesecond embodiment could be arranged such that the first and third doorsmove from the fully open position to the fairing position without movingvia the fully closed position. Thus, the first and third doors couldmove from the open position into the closed position simultaneously withdownwards rotation of the U-shaped frame, thereby moving the frame andthe doors into a fairing position as a unit. The first and third doorscould therefore move with two different modes of rotational movementsimultaneously.

Also, features from one embodiment could be used in another. Forexample, the panel section of the leg door of the seventh embodimentcould be used in conjunction with the leg door of the fifth embodiment,without the leg door being divided into other sections. Othermodifications will of course be apparent to the skilled person.

1. An aircraft landing gear and door assembly comprising a landing gearand a door, wherein (a) the door is moveable to an open position, inwhich at least part of an aperture is exposed, the landing gear beingable to be deployed through said aperture, (b) the door is moveable to aclosed position, in which the door is closed across said at least partof the aperture, and (c) at least a portion of the door is movable to afairing position in which it forms, with another part of the aircraftlanding gear and door assembly, a noise-reduction fairing assembly, themovement of the door to the fairing position including movement relativeto said another part of the aircraft landing gear and door assembly. 2.An assembly according to claim 1, wherein said another part of theaircraft landing gear and door assembly is at least partially defined bya structure mounted on the landing gear so that said another part of theaircraft landing gear and door assembly and said landing gear are causedto move together as a unit as the landing gear moves to a deployedposition.
 3. An assembly according to claim 1, wherein said another partof the aircraft landing gear and door assembly is connected to said atleast a portion of the door so that said another part of the aircraftlanding gear and door assembly and said at least a portion of the doorare caused to move together as a unit as the door moves to its fairingposition.
 4. An assembly according to claim 3, wherein said another partof the aircraft landing gear and door assembly is at least partiallydefined by another portion of the door.
 5. An assembly according toclaim 1, wherein the aircraft landing gear and door assembly comprises afurther door, the further door being moveable to an open position, inwhich a part of the aperture is exposed and moveable to a closedposition, in which the further door is closed across said part of theaperture.
 6. An assembly according to claim 5, wherein said another partof the aircraft landing gear and door assembly is at least partiallydefined by a portion of said further door.
 7. An assembly according toclaim 5, wherein the door and the further door define a pair of doors onopposite sides of the aperture.
 8. An assembly according to claim 1,wherein said another part of the aircraft landing gear and door assemblyis at least partially defined by a panel section.
 9. An assemblyaccording to claim 8, wherein the panel section is coupled to the door.10. An assembly according to claim 8, wherein the panel section ismounted on the landing gear.
 11. An assembly according to claim 1,wherein said at least a portion of the door is rotatable about an axissubstantially parallel to the length of the aircraft to move said atleast a portion of the door between the closed position and the openposition.
 12. An assembly according to claim 1, wherein the aircraftlanding gear and door assembly is so arranged that said relativemovement between said at least a portion of the door and said anotherpart of the aircraft landing gear and door assembly is movement aboutaxis, which when the door is in the open position is both transverse tothe length of the aircraft and substantially parallel to the door. 13.An assembly according to claim 1, wherein the aircraft landing gear anddoor assembly is so arranged that said relative movement between said atleast a portion of the door and said another part of the aircraftlanding gear and door assembly is movement about axis that issubstantially vertical.
 14. An assembly according to claim 1, whereinthe aircraft landing gear and door assembly is so arranged that saidrelative movement is about an axis that moves with the door when thedoor is moved between the open and closed positions.
 15. An assemblyaccording to claim 1, wherein the aircraft landing gear and doorassembly is so arranged that the movement of the door from the closed tothe open position and the movement of said at least a portion of thedoor to the fairing position are effected simultaneously for at leastpart of the respective movements.
 16. An assembly according to claim 15,wherein the aircraft landing gear and door assembly is so arranged thatthe movement of the door to the fully open position and the movement ofsaid at least a portion of the door to the fairing position are effectedsimultaneously.
 17. An assembly according to claim 15, wherein theaircraft landing gear and door assembly is so arranged that the start ofthe relative movement of said at least a portion of the door to thefairing position is delayed until the door has traveled beyond 50% ofthe distance from the closed position to the fully open position.
 18. Anassembly according to claim 1, wherein the aircraft landing gear anddoor assembly is so arranged that when the noise-reduction fairingassembly is formed and the landing gear is subjected to an airflow, thenoise-reduction fairing assembly diverts air in a substantiallyhorizontal direction.
 19. An assembly according to claim 1, wherein theaircraft landing gear and door assembly is so arranged that when thenoise-reduction fairing assembly is formed and the landing gear issubjected to an airflow, the noise-reduction fairing assembly splits theairflow so that first portion of the airflow is diverted in a firstdirection and a second portion of the airflow is diverted in a seconddifferent direction.
 20. An assembly according to claim 19, wherein theaircraft landing gear and door assembly is so arranged that thenoise-reduction fairing assembly, when formed, is generally in the formof a V-shaped fairing in front of the landing gear, thereby splittingthe airflow to either side of the landing gear.
 21. An aircraft landinggear and door assembly comprising a landing gear and a door, wherein (a)the door is moveable to an open position, in which at least part of anaperture is exposed, the landing gear being able to be deployed throughsaid aperture, (b) the door is moveable to a closed position, in whichthe door is closed across said at least part of the aperture, and (c) atleast a portion of the door is movable to a fairing position in which itforms at least part of a noise-reduction fairing, which is adapted sothat, when the landing gear is subjected to an airflow and said at leasta portion of the door is moved to the fairing position, thenoise-reduction fairing so formed splits the airflow so that a firstportion of the airflow is diverted in a first direction and a secondportion of the airflow is diverted in a second different direction. 22.An assembly according to claim 21, wherein the aircraft landing gear anddoor assembly is so arranged that the noise-reduction fairing, whenformed, is generally in the form of V-shaped fairing in front of thelanding gear, thereby splitting the airflow to either side of thelanding gear.
 23. A method of reducing noise caused by landing gear onan aircraft including a step of manufacturing an aircraft landing gearand door assembly according to claim
 1. 24. A method of reducing noisecaused by an extended landing gear in an aircraft during flying, theaircraft having an aircraft landing gear and door assembly comprising atleast one door and a landing gear, the method comprising the steps of:moving the at least one door from a closed position to an open positionto open at least partially an aperture; deploying the landing gear viathe aperture; and causing relative movement between at least a portionof the at least one door and another part of the aircraft landing gearand door assembly such that a noise-reduction fairing assembly is formedby said portion of the at least one door and said another part of theaircraft landing gear and door assembly, whereby noise from the landinggear during flying is reduced by the noise-reduction fairing assembly.25. A method according to claim 24, wherein the step of forming anoise-reduction fairing assembly is performed by causing relativemovement between a portion of the at least one door and a differentportion of a door that is moveable to a position for closing at least apart of the aperture.
 26. A method according to claim 25, wherein thestep of forming a noise reduction fairing assembly is performed bycausing relative movement between a portion of the at least one door anda different portion on the same door.
 27. A method according to claim25, wherein the step of forming a noise reduction fairing assembly isperformed by causing relative movement between a portion of the at leastone door and a portion of a different door that is moveable to aposition for closing a part of the aperture.
 28. A method according toclaim 24, wherein the step of forming a noise-reduction fairing assemblyis performed by causing relative movement between a portion of the atleast one door and a panel section mounted on the landing gear.